1. Field of the Invention
The present invention relates to two-arm transfer robots which are suitably used for horizontal transfer of disk-like works such as wafers under a vacuum condition in manufacture of semiconductors, for example.
2. Description of the Related Art
In manufacture of semiconductors, works are moved into and out of a number of process chambers. Specifically, works are moved between an atmospheric transfer module and each process chamber via an vacuum transfer module. As shown in FIG. 14, such a vacuum transfer module consists of a transport chamber 12 (to which the process chambers 11 are connected) and loadlocks 13 (connecting the transport chamber 12 to the atmospheric transfer module 20), for example. The loadlocks 13 have a first door 13a to the atmospheric transport module 20 and a second door 13b to the transport chamber 12. To move a work from the atmospheric transport module 20 into the loadlock 13, the first door 13a is opened, while the second door 13b is closed. Thus, the internal pressure of the loadlock 13 becomes atmospheric. Then, the first door 13a is closed, and the second door 13b are opened to move the work from the loadlock 13 into the transport chamber 12. At this stage, the internal pressure of the loadlock 13 becomes equal to that of the transport chamber 12 (that is, vacuum). Each process chamber 11 has a door 11a to the transport chamber 12, and opening the door 11a allows movement of works between the transport chamber 12 and the process chamber 11.
Transfer of works between the atmospheric transport module 20 and the loadlock 13 is implemented by a transfer robot on the side of the atmospheric transport module 20. Transfer of works between the loadlock 13 and the transport chamber 12, and between the transport chamber 12 and the process chamber 11 is implemented by a transfer robot placed in the transport chamber 12. The present invention relates to a transfer robot suitable for use in the transport chamber 12.
A conventional transfer robot of the above type is disclosed in JP-A-11 (1999)-33951, for example. As shown in FIG. 15, the conventional transfer robot includes two arm mechanisms 31, 32 mounted on a base 30. The base 30 is pivotable about a vertical shaft (or more appropriately, a vertical axis of the shaft). Each arm mechanism 31, 32 is provided with two parallelogram linkages connected to each other. As shown in FIG. 15, in each arm mechanism, a terminal link 35 is pivotably connected to two parallel rods. The terminal link member 35 supports a hand member 33 or 34 for carrying a plate-like work such as a wafer. When operated, the arm mechanisms 31, 32 can deform without interfering with each other, to move the respective terminal link members 35 horizontally along straight operation paths which are parallel to each other. Typically, such hand members are connected to the terminal links 35 via a connecting stay. When the arm mechanisms 31, 32 are operated, the hand members 33, 34 move forward or backward along predetermined paths Tr1, Tr2 which seem to coincide with each other as viewed in plan but are vertically spaced from each other, as shown in FIG. 16. Accordingly, the upper surfaces (wafer-carrying surfaces) of the respective hand members 33, 34 are disposed at different heights.
A work in the loadlock 13 is moved into the transport chamber 12 in the following manner. First, the base 30 is turned about the vertical shaft through an appropriate angle to direct the hand members 33, 34 toward the loadlock 13. Then, one of the hand members 33, 34 is extended into the loadlock 13, through the second door 13b, to pick up the work. Finally, the hand member 33 or 34 is drawn back into the transport chamber 12.
The work brought into the transport chamber 12 can be moved further into the process chambers 11 as follows. First, the base 30 is turned about to direct the hand members 33, 34 toward the selected one of the process chambers 11. Then, the hand member 33 or 34 carrying the work is extended into the process chamber 11 through the door 11a, to place the work in the chamber 11. Finally, the hand member 33 or 34 is drawn back into the transport chamber 12. As readily understood, after the treatment of the work in the process chamber 11 is over, the work is transferred back in the same manner as described above, from the process chamber 11 to the transport chamber 12, and to the loadlock 13.
The transfer robot described above has two hand members 33, 34 that are independently operable. With such an arrangement, works can be moved into and out of the process chamber 11 efficiently. For instance, it is possible, with the door 11a kept open, to take a processed work out from the chamber 11 by one hand member, while holding another work to be processed near the chamber 11 by the other hand so that this work can be put into the chamber 11 immediately after the processed work is out.
In the conventional transfer robot, the paths Tr1, Tr2 for the hand members 33, 34 are vertically spaced from each other, as noted above. Therefore, as seen from FIG. 16, the door 11a of each process chamber 11 needs to have a rather large vertical dimension to accommodate the two paths Tr1, Tr2 of different heights.
However, a large opening of the door 11a may cause irregular and disordered flow of air in the process chamber. Such turbulence may impede uniform surface treatment for a wafer.